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La Gerche A, Wasfy MM, Brosnan MJ, Claessen G, Fatkin D, Heidbuchel H, Baggish AL, Kovacic JC. The Athlete's Heart-Challenges and Controversies: JACC Focus Seminar 4/4. J Am Coll Cardiol 2022; 80:1346-1362. [PMID: 36075838 DOI: 10.1016/j.jacc.2022.07.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 07/18/2022] [Accepted: 07/21/2022] [Indexed: 12/11/2022]
Abstract
Regular exercise promotes structural, functional, and electrical remodeling of the heart, often referred to as the "athlete's heart," with intense endurance sports being associated with the greatest degree of cardiac remodeling. However, the extremes of exercise-induced cardiac remodeling are potentially associated with uncommon side effects. Atrial fibrillation is more common among endurance athletes and there is speculation that other arrhythmias may also be more prevalent. It is yet to be determined whether this arrhythmic susceptibility is a result of extreme exercise remodeling, genetic predisposition, or other factors. Gender may have the greatest influence on the cardiac response to exercise, but there has been far too little research directed at understanding differences in the sportsman's vs sportswoman's heart. Here in part 4 of a 4-part seminar series, the controversies and ambiguities regarding the athlete's heart, and in particular, its arrhythmic predisposition, genetic, and gender influences are reviewed in depth.
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Affiliation(s)
- Andre La Gerche
- Clinical Research Domain, Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia; National Centre for Sports Cardiology, Fitzroy, Victoria, Australia; Cardiology Department, St Vincent's Hospital Melbourne, Fitzroy, Victoria, Australia.
| | - Meagan M Wasfy
- Division of Cardiology, Massachusetts General Hospital, Boston, Massachusetts, USA; Cardiovascular Performance Program, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Maria J Brosnan
- National Centre for Sports Cardiology, Fitzroy, Victoria, Australia; Cardiology Department, St Vincent's Hospital Melbourne, Fitzroy, Victoria, Australia
| | - Guido Claessen
- Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium; Department of Cardiovascular Diseases, University Hospitals Leuven, Leuven, Belgium
| | - Diane Fatkin
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; School of Clinical Medicine, Faculty of Medicine and Health, UNSW Sydney, Kensington, New South Wales, Australia; Cardiology Department, St Vincent's Hospital, Darlinghurst, New South Wales, Australia
| | - Hein Heidbuchel
- Antwerp University Hospital, Department of Cardiology, Antwerp, Belgium; Cardiovascular Sciences, Antwerp University, Antwerp, Belgium
| | - Aaron L Baggish
- Division of Cardiology, Massachusetts General Hospital, Boston, Massachusetts, USA; Cardiovascular Performance Program, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Jason C Kovacic
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; School of Clinical Medicine, Faculty of Medicine and Health, UNSW Sydney, Kensington, New South Wales, Australia; Cardiology Department, St Vincent's Hospital, Darlinghurst, New South Wales, Australia; Cardiovascular Research Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
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2
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Hedge ET, Patterson CA, Mastrandrea CJ, Sonjak V, Hajj-Boutros G, Faust A, Morais JA, Hughson RL. Implementation of exercise countermeasures during spaceflight and microgravity analogue studies: Developing countermeasure protocols for bedrest in older adults (BROA). Front Physiol 2022; 13:928313. [PMID: 36017336 PMCID: PMC9395735 DOI: 10.3389/fphys.2022.928313] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 06/27/2022] [Indexed: 12/18/2022] Open
Abstract
Significant progress has been made in the development of countermeasures to attenuate the negative consequences of prolonged exposure to microgravity on astronauts’ bodies. Deconditioning of several organ systems during flight includes losses to cardiorespiratory fitness, muscle mass, bone density and strength. Similar deconditioning also occurs during prolonged bedrest; any protracted time immobile or inactive, especially for unwell older adults (e.g., confined to hospital beds), can lead to similar detrimental health consequences. Due to limitations in physiological research in space, the six-degree head-down tilt bedrest protocol was developed as ground-based analogue to spaceflight. A variety of exercise countermeasures have been tested as interventions to limit detrimental changes and physiological deconditioning of the musculoskeletal and cardiovascular systems. The Canadian Institutes of Health Research and the Canadian Space Agency recently provided funding for research focused on Understanding the Health Impact of Inactivity to study the efficacy of exercise countermeasures in a 14-day randomized clinical trial of six-degree head-down tilt bedrest study in older adults aged 55–65 years old (BROA). Here we will describe the development of a multi-modality countermeasure protocol for the BROA campaign that includes upper- and lower-body resistance exercise and head-down tilt cycle ergometry (high-intensity interval and continuous aerobic exercise training). We provide reasoning for the choice of these modalities following review of the latest available information on exercise as a countermeasure for inactivity and spaceflight-related deconditioning. In summary, this paper sets out to review up-to-date exercise countermeasure research from spaceflight and head-down bedrest studies, whilst providing support for the proposed research countermeasure protocols developed for the bedrest study in older adults.
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Affiliation(s)
- Eric T. Hedge
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON, Canada
- Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | | | | | - Vita Sonjak
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - Guy Hajj-Boutros
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - Andréa Faust
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - José A. Morais
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
- Division of Geriatric Medicine, McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - Richard L. Hughson
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON, Canada
- *Correspondence: Richard L. Hughson,
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3
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Ogoh S, Hirasawa A, Shibata S. Influence of head-up tile and lower body negative pressure on the internal jugular vein. Physiol Rep 2022; 10:e15248. [PMID: 35581747 PMCID: PMC9114655 DOI: 10.14814/phy2.15248] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 03/16/2022] [Accepted: 03/17/2022] [Indexed: 06/15/2023] Open
Abstract
Head-up tilt (HUT)-induced gravitational stress causes collapse of the internal jugular vein (IJV) by decreasing central blood volume and through mass-effect from the surrounding tissues. Besides HUT, lower body negative pressure (LBNP) is used to stimulate orthostatic stress as an experimental model. Compared to HUT, LBNP has less of a gravitational effect because of the supine position; therefore, we hypothesized that LBNP causes less of a decrease in the cross-sectional area of the IJV compared to HUT. We tested the hypothesis by measuring the cross-sectional area of the IJV using B-mode ultrasonography while inducing orthostatic stress at levels of -40 mmHg LBNP and 60° HUT. The cross-sectional area of IJV decreased from the resting baseline during both LBNP and HUT trials, but the LBNP-induced decrease in the cross-sectional area of IJV was smaller than that of HUT (right, -45% ± 49% vs. -78% ± 27%, p = 0.008; left, -49% ± 27% vs. -78% ± 20%, p = 0.004). Since changes in venous outflow may affect cerebral arterial circulation, the findings of the present study suggest that orthostatic stress induced by different techniques modulates cerebral blood flow regulation through its effect on venous outflow.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical EngineeringToyo UniversitySaitamaJapan
- Neurovascular Research LaboratoryFaculty of Life Sciences and EducationUniversity of South WalesPontypriddUK
| | - Ai Hirasawa
- Department of Health and WelfareFaculty of Health SciencesKyorin UniversityTokyoJapan
| | - Shigeki Shibata
- Department of Physical TherapyFaculty of Health ScienceKyorin UniversityTokyoJapan
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4
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Dikshit MB. Cardiovascular Responses to Commonly Used Tests in and Outside of the Laboratory Settings. ANNALS OF THE NATIONAL ACADEMY OF MEDICAL SCIENCES (INDIA) 2022. [DOI: 10.1055/s-0042-1744391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
AbstractSeveral tests are available for assessing cardiovascular response to various interventions which may be given in the laboratory, or outside of it in the field. The tests are meant to excite or deactivate cardiovascular and other sensory receptors which signal the central mechanisms. They have been found useful in generating data to study cardiovascular effects on subjects exposed to specialized physical training (e.g., athletes), in the evaluation of people engaged in special occupations such as pilots, astronauts, and other military personnel, and in training undergraduate and postgraduate students. If the response does not fit into the physiological norm, it may reflect a temporary aberration, or a more serious defect in the cardiovascular control mechanism because of disease. Interpretation of data generated may vary between various operators/observers. Here, an attempt has been made to bring out responses of the cardiovascular system to the commonly used tests, and their applicability in clinical situations.
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Affiliation(s)
- Mohan B. Dikshit
- Formerly Department of Physiology and Clinical Physiology, College of Medicine and Sultan Qaboos Hospital, Sultan Qaboos University, Muscat, Oman
- Formerly Department of Physiology, Maharashtra Institute of Medical Education and Research Medical College, Pune, Maharashtra, India
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5
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Stute NL, Stickford JL, Province VM, Augenreich MA, Ratchford SM, Stickford ASL. COVID-19 is getting on our nerves: sympathetic neural activity and haemodynamics in young adults recovering from SARS-CoV-2. J Physiol 2021; 599:4269-4285. [PMID: 34174086 PMCID: PMC8447023 DOI: 10.1113/jp281888#support-information-section] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 06/16/2021] [Indexed: 11/10/2023] Open
Abstract
KEY POINTS The impact of SARS-CoV-2 infection on autonomic and cardiovascular function in otherwise healthy individuals is unknown. For the first time it is shown that young adults recovering from SARS-CoV-2 have elevated resting sympathetic activity, but similar heart rate and blood pressure, compared with control subjects. Survivors of SARS-CoV-2 also exhibit similar sympathetic nerve activity and haemodynamics, but decreased pain perception, during a cold pressor test compared with healthy controls. Further, these individuals display higher sympathetic nerve activity throughout an orthostatic challenge, as well as an exaggerated heart rate response to orthostasis. If similar autonomic dysregulation, like that found here in young individuals, is present in older adults following SARS-CoV-2 infection, there may be substantial adverse implications for cardiovascular health. ABSTRACT The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can elicit systemic adverse physiological effects. However, the impact of SARS-CoV-2 on autonomic and cardiovascular function in otherwise healthy individuals remains unclear. Young adults who tested positive for SARS-CoV-2 (COV+; n = 16, 8 F) visited the laboratory 35 ± 16 days following diagnosis. Muscle sympathetic nerve activity (MSNA), systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) were measured in participants at rest and during a 2 min cold pressor test (CPT) and 5 min each at 30° and 60° head-up tilt (HUT). Data were compared with age-matched healthy controls (CON; n = 14, 9 F). COV+ participants (18.2 ± 6.6 bursts min-1 ) had higher resting MSNA burst frequency compared with CON (12.7 ± 3.4 bursts min-1 ) (P = 0.020), as well as higher MSNA burst incidence and total activity. Resting HR, SBP and DBP were not different. During CPT, there were no differences in MSNA, HR, SBP or DBP between groups. COV+ participants reported less pain during the CPT compared with CON (5.7 ± 1.8 vs. 7.2 ± 1.9 a.u., P = 0.036). MSNA was higher in COV+ compared with CON during HUT. There was a group-by-position interaction in MSNA burst incidence, as well as HR, in response to HUT. These results indicate resting sympathetic activity, but not HR or BP, may be elevated following SARS-CoV-2 infection. Further, cardiovascular and perceptual responses to physiological stress may be altered, including both exaggerated (orthostasis) and suppressed (pain perception) responses, compared with healthy young adults.
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Affiliation(s)
- Nina L. Stute
- Department of Health & Exercise ScienceAppalachian State UniversityBooneNCUSA
| | | | - Valesha M. Province
- Department of Health & Exercise ScienceAppalachian State UniversityBooneNCUSA
| | - Marc A. Augenreich
- Department of Health & Exercise ScienceAppalachian State UniversityBooneNCUSA
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6
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Stute NL, Stickford JL, Province VM, Augenreich MA, Ratchford SM, Stickford ASL. COVID-19 is getting on our nerves: sympathetic neural activity and haemodynamics in young adults recovering from SARS-CoV-2. J Physiol 2021; 599:4269-4285. [PMID: 34174086 PMCID: PMC8447023 DOI: 10.1113/jp281888] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 06/16/2021] [Indexed: 12/19/2022] Open
Abstract
Key points The impact of SARS‐CoV‐2 infection on autonomic and cardiovascular function in otherwise healthy individuals is unknown. For the first time it is shown that young adults recovering from SARS‐CoV‐2 have elevated resting sympathetic activity, but similar heart rate and blood pressure, compared with control subjects. Survivors of SARS‐CoV‐2 also exhibit similar sympathetic nerve activity and haemodynamics, but decreased pain perception, during a cold pressor test compared with healthy controls. Further, these individuals display higher sympathetic nerve activity throughout an orthostatic challenge, as well as an exaggerated heart rate response to orthostasis. If similar autonomic dysregulation, like that found here in young individuals, is present in older adults following SARS‐CoV‐2 infection, there may be substantial adverse implications for cardiovascular health.
Abstract The novel severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) can elicit systemic adverse physiological effects. However, the impact of SARS‐CoV‐2 on autonomic and cardiovascular function in otherwise healthy individuals remains unclear. Young adults who tested positive for SARS‐CoV‐2 (COV+; n = 16, 8 F) visited the laboratory 35 ± 16 days following diagnosis. Muscle sympathetic nerve activity (MSNA), systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) were measured in participants at rest and during a 2 min cold pressor test (CPT) and 5 min each at 30° and 60° head‐up tilt (HUT). Data were compared with age‐matched healthy controls (CON; n = 14, 9 F). COV+ participants (18.2 ± 6.6 bursts min−1) had higher resting MSNA burst frequency compared with CON (12.7 ± 3.4 bursts min−1) (P = 0.020), as well as higher MSNA burst incidence and total activity. Resting HR, SBP and DBP were not different. During CPT, there were no differences in MSNA, HR, SBP or DBP between groups. COV+ participants reported less pain during the CPT compared with CON (5.7 ± 1.8 vs. 7.2 ± 1.9 a.u., P = 0.036). MSNA was higher in COV+ compared with CON during HUT. There was a group‐by‐position interaction in MSNA burst incidence, as well as HR, in response to HUT. These results indicate resting sympathetic activity, but not HR or BP, may be elevated following SARS‐CoV‐2 infection. Further, cardiovascular and perceptual responses to physiological stress may be altered, including both exaggerated (orthostasis) and suppressed (pain perception) responses, compared with healthy young adults. The impact of SARS‐CoV‐2 infection on autonomic and cardiovascular function in otherwise healthy individuals is unknown. For the first time it is shown that young adults recovering from SARS‐CoV‐2 have elevated resting sympathetic activity, but similar heart rate and blood pressure, compared with control subjects. Survivors of SARS‐CoV‐2 also exhibit similar sympathetic nerve activity and haemodynamics, but decreased pain perception, during a cold pressor test compared with healthy controls. Further, these individuals display higher sympathetic nerve activity throughout an orthostatic challenge, as well as an exaggerated heart rate response to orthostasis. If similar autonomic dysregulation, like that found here in young individuals, is present in older adults following SARS‐CoV‐2 infection, there may be substantial adverse implications for cardiovascular health.
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Affiliation(s)
- Nina L Stute
- Department of Health & Exercise Science, Appalachian State University, Boone, NC, USA
| | - Jonathon L Stickford
- Department of Health & Exercise Science, Appalachian State University, Boone, NC, USA
| | - Valesha M Province
- Department of Health & Exercise Science, Appalachian State University, Boone, NC, USA
| | - Marc A Augenreich
- Department of Health & Exercise Science, Appalachian State University, Boone, NC, USA
| | - Stephen M Ratchford
- Department of Health & Exercise Science, Appalachian State University, Boone, NC, USA
| | - Abigail S L Stickford
- Department of Health & Exercise Science, Appalachian State University, Boone, NC, USA
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7
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Cheung CP, Coates AM, Millar PJ, Burr JF. Habitual cannabis use is associated with altered cardiac mechanics and arterial stiffness, but not endothelial function in young healthy smokers. J Appl Physiol (1985) 2021; 130:660-670. [PMID: 33444123 DOI: 10.1152/japplphysiol.00840.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Cigarette smoking is among the most detrimental behaviors to cardiovascular health, resulting in arterial stiffening, endothelial dysfunction, and structural/functional alterations to the myocardium. Similar to cigarettes, cannabis is commonly smoked, and next to alcohol, is the most commonly used recreational substance in the world. Despite this, little is known about the long-term cardiovascular effects of smoking cannabis. This study explored the associations of cardiovascular structure and function with cannabis use in ostensibly healthy young participants (n = 35). Using echocardiography, carotid-femoral pulse wave velocity (cfPWV), and brachial flow-mediated dilation (FMD), we performed a cross-sectional assessment of cardiovascular function in cannabis users (n = 18) and controls (n = 17). There were no differences in cardiac morphology or traditional resting measures of systolic or diastolic function between cannabis users and controls (all P > 0.05), whereas cannabis users demonstrated reduced peak apical rotation compared with controls (cannabis users: 5.5 ± 3.8, controls: 9.6 ± 1.5; P = 0.02). Cannabis users had higher cfPWV compared with controls (cannabis users: 5.8 ± 0.6 m/s, controls: 5.3 ± 0.7 m/s; P = 0.05), whereas FMD was similar between cannabis users and controls (cannabis users: 8.3 ± 3.3%, controls: 6.8 ± 3.6%; P = 0.7). Young, healthy, and cannabis users demonstrate altered cardiac mechanics and greater aortic stiffness. Further studies should explore causal links between cannabis smoking and altered cardiovascular function.NEW & NOTEWORTHY Recreational cannabis is the most widely used substance in the world, other than alcohol. Yet, the effects of cannabis use on cardiovascular function and health are not well understood. Our cross-sectional data demonstrate that young, ostensibly healthy cannabis users have greater arterial stiffness and altered cardiac mechanics compared to nonusers. These findings suggest that cannabis users may be at greater risk of the development of future cardiovascular disease.
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Affiliation(s)
- Christian P Cheung
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Alexandra M Coates
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Philip J Millar
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Jamie F Burr
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
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8
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Sarma S, Howden E, Lawley J, Samels M, Levine BD. Central Command and the Regulation of Exercise Heart Rate Response in Heart Failure With Preserved Ejection Fraction. Circulation 2020; 143:783-789. [PMID: 33205661 DOI: 10.1161/circulationaha.120.048338] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Chronotropic incompetence is common in heart failure with preserved ejection fraction (HFpEF) and is linked to impaired aerobic capacity. Whether upstream autonomic signaling pathways responsible for raising exercise heart rate are impaired in HFpEF is unknown. We investigated the integrity of central command and muscle metaboreceptor function, 2 predominant mechanisms responsible for exertional increases in heart rate, in patients with HFpEF and senior controls. METHODS Fourteen healthy senior controls (7 men, 7 women) and 20 carefully screened patients with HFpEF (8 men, 12 women) underwent cardiopulmonary exercise testing (peak Vo2) and static handgrip exercise at 40% of maximal voluntary contraction to fatigue with postexercise circulatory arrest for 2 minutes to assess central command and metaboreceptor function, respectively. RESULTS Peak Vo2 (13.1±3.4 versus 22.7±4.0 mL/kg/min; P<0.001) and heart rate (122±20 versus 155±14 bpm; P<0.001) were lower in patients with HFpEF than senior controls. There were no significant differences in peak heart rate response during static handgrip between groups (patients with HFpEF versus controls: 90±13 versus 93±10 bpm; P=0.49). Metaboreceptor function, defined as mean arterial blood pressure at the end of postexercise circulatory arrest, was not significantly different between groups. CONCLUSIONS Central command (vagally mediated) and metaboreceptor function (sympathetically mediated) in patients with HFpEF were not different from those in healthy senior controls despite significantly lower peak whole-body exercise heart rates. These results demonstrate key reflex autonomic pathways regulating exercise heart rate responsiveness are intact in HFpEF.
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Affiliation(s)
- Satyam Sarma
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas (S.S., M.S., B.D.L.).,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas (S.S., B.D.L.)
| | - Erin Howden
- Baker Heart and Diabetes Institute, Melbourne, Australia (E.H.)
| | - Justin Lawley
- Department of Sport Science, University of Innsbruck, Austria (J.L.)
| | - Mitchel Samels
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas (S.S., M.S., B.D.L.)
| | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas (S.S., M.S., B.D.L.).,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas (S.S., B.D.L.)
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Tarasova OS, Kalenchuk VU, Borovik AS, Golubinskaya VO, Delp MD, Vinogradova OL. Simulated Microgravity Induces Regionally Distinct Neurovascular and Structural Remodeling of Skeletal Muscle and Cutaneous Arteries in the Rat. Front Physiol 2020; 11:675. [PMID: 32695017 PMCID: PMC7339929 DOI: 10.3389/fphys.2020.00675] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 05/26/2020] [Indexed: 01/10/2023] Open
Abstract
Introduction: Mechanical forces and sympathetic influences are key determinants of vascular structure and function. This study tested the hypothesis that hindlimb unloading (HU) exerts diverse effects on forelimb and hindlimb small arteries of rats in functionally different regions of the skeletal muscle and skin. Methods: Male Wistar rats were subjected to HU for 2 weeks, then skeletal muscle arteries (deep brachial and sural) and skin arteries (median and saphenous) were examined in vitro using wire myography or isobaric perfusion and glyoxylic acid staining. Results: HU increased lumen diameter of both forelimb arteries but decreased diameter of the sural artery; the saphenous artery diameter was not affected. Following HU, maximal contractile responses to noradrenaline and serotonin increased in the forelimb but decreased in the hindlimb skeletal muscle feed arteries with no change in skin arteries; all region-specific alterations persisted after endothelium removal. HU increased the sensitivity to vasoconstrictors in the saphenous artery but not in the sural artery. In the saphenous artery, initially high sympathetic innervation density was reduced by HU, sparse innervation in the sural artery was not affected. Electrical stimulation of periarterial sympathetic nerves in isobarically perfused segments of the saphenous artery demonstrated a two-fold decrease of the contractile responses in HU rats compared to that of controls. Conclusion: HU induces contrasting structural and functional adaptations in forelimb and hindlimb skeletal muscle arteries. Additionally, HU had diverse effects in two hindlimb vascular regions. Hyper-sensitivity of the saphenous artery to vasoconstrictors appears to result from the shortage of trophic sympathetic influence. Importantly, HU impaired sympathetically induced arterial vasoconstriction, consistent with the decreased sympathetic constrictor response in humans following space flight.
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Affiliation(s)
- Olga S Tarasova
- State Research Center of the Russian Federation, Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia
- Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia
| | | | - Anatoly S Borovik
- State Research Center of the Russian Federation, Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia
| | | | - Michael D Delp
- Department of Nutrition, Food and Exercise Sciences, College of Human Sciences, Florida State University, Tallahassee, FL, United States
| | - Olga L Vinogradova
- State Research Center of the Russian Federation, Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia
- Faculty of Basic Medicine, M.V. Lomonosov Moscow State University, Moscow, Russia
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10
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Chen W, Chen Z, Xiang Y, Deng C, Zhang H, Wang J. Simultaneous influence of sympathetic autonomic stress on Schlemm's canal, intraocular pressure and ocular circulation. Sci Rep 2019; 9:20060. [PMID: 31882796 PMCID: PMC6934569 DOI: 10.1038/s41598-019-56562-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 12/12/2019] [Indexed: 11/09/2022] Open
Abstract
This study aimed to investigate changes in Schlemm's canal, intraocular pressure and ocular blood circulation following the activation of the sympathetic nervous system. Twenty healthy volunteers were enrolled in this study. The cold pressor test (CPT) was adopted. Cross-sectional area of Schlemm's canal (SCAR), superficial and deep retinal vessel densities (s-RVD;d-RVD), pupil diameter (PD), intraocular pressure (IOP), mean ocular perfusion pressure (MOPP) and heart rate variability (HRV) were measured at three time-points: baseline (T0) and 5 min (T1) and 10 min (T2) after the CPT. After cold stimulation, LF/HF index (the ratio of low frenquency and high frenquency) increased significantly. IOP decreased from 16.9 ± 1.9 mmHg at baseline to 16.4 ± 2.7 mmHg at T1 and to 15.2 ± 2.7 mmHg at T2. The nasal cross-sectional area of SCAR (SCAR-n) increased from 6283.9 ± 2696.2 µm2 at baseline to 8392.9 ± 3258.7 µm2 at T1 and to 10422.0 ± 3643.8 µm2 at T2. The temporal cross-sectional area of SCAR (SCAR-t) increased from 6414.5 ± 2218.7 µm2 at baseline to 8610.8 ± 2317.1 µm2 at T1 and to 11544.0 ± 4129.2 µm2 at T2. The expansion of Schlemm's canal was observed after the CPT might be caused by sympathetic nerve stimulation, subsequently leading to decreased IOP.
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Affiliation(s)
- Wei Chen
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhiqi Chen
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yan Xiang
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Chaohua Deng
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hong Zhang
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Junming Wang
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
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WASFY MEAGANM, WEINER RORYB, WANG FRANCIS, BERKSTRESSER BRANT, DELUCA JAMES, HUTTER ADOLPHM, PICARD MICHAELH, BAGGISH AARONL. Myocardial Adaptations to Competitive Swim Training. Med Sci Sports Exerc 2019; 51:1987-1994. [DOI: 10.1249/mss.0000000000002022] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Andreev-Andrievskiy AA, Popova AS, Lagereva EA, Vinogradova OL. Fluid shift versus body size: changes of hematological parameters and body fluid volume in hindlimb-unloaded mice, rats and rabbits. ACTA ACUST UNITED AC 2018; 221:jeb.182832. [PMID: 29950449 DOI: 10.1242/jeb.182832] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Accepted: 06/11/2018] [Indexed: 01/12/2023]
Abstract
The cardiovascular system is adapted to gravity, and reactions to the loss of gravity in space are presumably dependent on body size. The dependence of hematological parameters and body fluid volume on simulated microgravity have never been studied as an allometric function before. Thus, we estimated red blood cell (RBC), blood and extracellular fluid volume in hindlimb-unloaded (HLU) or control (attached) mice, rats and rabbits. RBC decrease was found to be size independent, and the allometric dependency for RBC loss in HLU and control animals shared a common power (-0.054±0.008) but a different Y0 coefficient (8.66±0.40 and 10.73±0.49, respectively, P<0.05). Blood volume in HLU animals was unchanged compared with that of controls, disregarding body size. The allometric dependency of interstitial fluid volume in HLU and control mice shared Y0 (1.02±0.09) but had different powers N (0.708±0.017 and 0.648±0.016, respectively, P<0.05), indicating that the interstitial fluid volume increase during hindlimb unloading is more pronounced in larger animals. Our data underscore the importance of size-independent mechanisms of cardiovascular adaptation to weightlessness. Despite the fact that the use of mice hampers application of a straightforward translational approach, this species is useful for gravitational biology as a tool to investigate size-independent mechanisms of mammalian adaptation to microgravity.
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Affiliation(s)
- Alexander A Andreev-Andrievskiy
- Institute of Biomedical Problems, Russian Academy of Sciences, Moscow 123007, Russia .,M.V. Lomonosov Moscow State University, Biology Faculty, Moscow 119991, Russia
| | - Anfisa S Popova
- Institute of Biomedical Problems, Russian Academy of Sciences, Moscow 123007, Russia.,M.V. Lomonosov Moscow State University, Biology Faculty, Moscow 119991, Russia
| | - Evgeniia A Lagereva
- Institute of Biomedical Problems, Russian Academy of Sciences, Moscow 123007, Russia
| | - Olga L Vinogradova
- Institute of Biomedical Problems, Russian Academy of Sciences, Moscow 123007, Russia
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Myers CM, Kim JS, Musilli M, McCully K, Florian JP. Effects of Resting, Consecutive, Long-Duration Water Immersions on Neuromuscular Endurance in Well-Trained Males. Front Physiol 2018; 9:977. [PMID: 30100879 PMCID: PMC6072852 DOI: 10.3389/fphys.2018.00977] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 07/03/2018] [Indexed: 11/22/2022] Open
Abstract
Purpose: This study examined the effects of repeated long-duration water immersions (WI)s at 1.35 atmospheres absolute (ATA) on neuromuscular endurance performance. We hypothesized that, following 5 days of consecutive, resting, long-duration WIs, neuromuscular endurance performance would decrease. Methods: Fifteen well-trained, male subjects completed five consecutive 6-h resting WIs with 18-h surface intervals during the dive week while breathing compressed air at 1.35 ATA. Skeletal muscle endurance performance was assessed before and after each WI, and 24 and 72 h after the final WI. Muscular endurance assessments included 40% maximum handgrip endurance (MHE) and 50-repetition maximal isokinetic knee extensions. Near infrared spectroscopy was used to measure muscle oxidative capacity of the vastus lateralis and localized muscle tissue oxygenation of the vastus lateralis and flexor carpi radialis. Simultaneously, brachioradialis neuromuscular activation was measured by surface electromyography. Results: A 24.9% increase (p = 0.04) in the muscle oxidative capacity rate constant (k) occurred on WI 4 compared to baseline. No changes occurred in 40% MHE time to exhaustion or rate of fatigue or total work performed for the 50-repetition maximal isokinetic knee extension. The first quartile of deoxygenated hemoglobin concentration showed a 6 and 35% increase on WIs 3 and 5 (p = 0.026) with second quartile increases of 9 and 32% on WIs 3 and 5 (p = 0.049) during the 40% MHE testing when compared to WI 1. Conclusion: Our specific WI protocol resulted in no change to muscular endurance and oxygen kinetics in load bearing and non-load bearing muscles.
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Affiliation(s)
- Christopher M Myers
- Department of Nutrition, Food and Exercise Sciences, Florida State University, Tallahassee, FL, United States.,United States Navy Experimental Diving Unit, Panama City Beach, FL, United States
| | - Jeong-Su Kim
- Department of Nutrition, Food and Exercise Sciences, Florida State University, Tallahassee, FL, United States
| | - Megan Musilli
- United States Navy Experimental Diving Unit, Panama City Beach, FL, United States
| | - Kevin McCully
- Department of Kinesiology, University of Georgia, Athens, GA, United States
| | - John P Florian
- Department of Nutrition, Food and Exercise Sciences, Florida State University, Tallahassee, FL, United States.,United States Navy Experimental Diving Unit, Panama City Beach, FL, United States
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14
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Eckberg DL, Cooke WH, Diedrich A, Biaggioni I, Buckey JC, Pawelczyk JA, Ertl AC, Cox JF, Kuusela TA, Tahvanainen KUO, Mano T, Iwase S, Baisch FJ, Levine BD, Adams-Huet B, Robertson D, Blomqvist CG. Respiratory modulation of human autonomic function on Earth. J Physiol 2016; 594:5611-27. [PMID: 27028958 PMCID: PMC5043049 DOI: 10.1113/jp271654] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 03/14/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS We studied healthy supine astronauts on Earth with electrocardiogram, non-invasive arterial pressure, respiratory carbon dioxide concentrations, breathing depth and sympathetic nerve recordings. The null hypotheses were that heart beat interval fluctuations at usual breathing frequencies are baroreflex mediated, that they persist during apnoea, and that autonomic responses to apnoea result from changes of chemoreceptor, baroreceptor or lung stretch receptor inputs. R-R interval fluctuations at usual breathing frequencies are unlikely to be baroreflex mediated, and disappear during apnoea. The subjects' responses to apnoea could not be attributed to changes of central chemoreceptor activity (hypocapnia prevailed); altered arterial baroreceptor input (vagal baroreflex gain declined and muscle sympathetic nerve burst areas, frequencies and probabilities increased, even as arterial pressure climbed to new levels); or altered pulmonary stretch receptor activity (major breathing frequency and tidal volume changes did not alter vagal tone or sympathetic activity). Apnoea responses of healthy subjects may result from changes of central respiratory motoneurone activity. ABSTRACT We studied eight healthy, supine astronauts on Earth, who followed a simple protocol: they breathed at fixed or random frequencies, hyperventilated and then stopped breathing, as a means to modulate and expose to view important, but obscure central neurophysiological mechanisms. Our recordings included the electrocardiogram, finger photoplethysmographic arterial pressure, tidal volume, respiratory carbon dioxide concentrations and peroneal nerve muscle sympathetic activity. Arterial pressure, vagal tone and muscle sympathetic outflow were comparable during spontaneous and controlled-frequency breathing. Compared with spontaneous, 0.1 and 0.05 Hz breathing, however, breathing at usual frequencies (∼0.25 Hz) lowered arterial baroreflex gain, and provoked smaller arterial pressure and R-R interval fluctuations, which were separated by intervals that were likely to be too short and variable to be attributed to baroreflex physiology. R-R interval fluctuations at usual breathing frequencies disappear during apnoea, and thus cannot provide evidence for the existence of a central respiratory oscillation. Apnoea sets in motion a continuous and ever changing reorganization of the relations among stimulatory and inhibitory inputs and autonomic outputs, which, in our study, could not be attributed to altered chemoreceptor, baroreceptor, or pulmonary stretch receptor activity. We suggest that responses of healthy subjects to apnoea are driven importantly, and possibly prepotently, by changes of central respiratory motoneurone activity. The companion article extends these observations and asks the question, Might terrestrial responses to our 20 min breathing protocol find expression as long-term neuroplasticity in serial measurements made over 20 days during and following space travel?
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Affiliation(s)
- Dwain L Eckberg
- Departments of Medicine and Physiology, Hunter Holmes McGuire Department of Veterans Affairs, Medical Center and Virginia Commonwealth University School of Medicine, Richmond, VA, USA.
| | - William H Cooke
- Department of Kinesiology, Health, and Nutrition, University of Texas at San Antonio, San Antonio, TX, USA
| | - André Diedrich
- Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, TN, USA
| | - Italo Biaggioni
- Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, TN, USA
| | - Jay C Buckey
- Dartmouth Hitchcock Medical Center, Lebanon, NH, USA
| | - James A Pawelczyk
- Department of Physiology, Pennsylvania State University, University Park and Hershey, PA, USA
| | - Andrew C Ertl
- Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, TN, USA
| | - James F Cox
- Departments of Medicine and Physiology, Hunter Holmes McGuire Department of Veterans Affairs, Medical Center and Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - Tom A Kuusela
- Department of Physics, University of Turku, Turku, Finland
| | - Kari U O Tahvanainen
- Department of Clinical Physiology and Nuclear Medicine, South Karelia Central Hospital, Lappeenranta, Finland
| | - Tadaaki Mano
- Gifu University of Medical Science, 795-1 Nagamine Ichihiraga, Seki, Gifu, 501-3892, Japan
| | - Satoshi Iwase
- Department of Physiology, Aichi Medical University, Aichi, Japan
| | | | - Benjamin D Levine
- Department of Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, TX, USA
| | | | - David Robertson
- Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, TN, USA
| | - C Gunnar Blomqvist
- Department of Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA
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15
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Sympathetic neural and cardiovascular responses during static handgrip exercise in women with a history of hypertensive pregnancy. Clin Auton Res 2016; 26:395-405. [PMID: 27506589 DOI: 10.1007/s10286-016-0372-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 07/26/2016] [Indexed: 02/07/2023]
Abstract
PURPOSE Women with a history of hypertensive pregnancy are at greater risk for future cardiovascular events; however, the mechanisms for this increased risk are unknown. Evidence suggests that an exercise stimulus unmasks latent hypertensive tendencies, identifying individuals at the greatest risk for developing cardiovascular disease. The current study examined the hypothesis that women with a hypertensive pregnancy history exhibit an augmented exercise pressor response. METHODS Normotensive women with a history of healthy pregnancy (CON; n = 9) and hypertensive pregnancy (HP+; n = 12) were studied during the mid-luteal phase of the menstrual cycle. Heart rate (HR), systolic and diastolic blood pressure (SBP, DBP), and muscle sympathetic nerve activity (MSNA) were measured during a cold pressor test (CPT), and, following a sufficient period of recovery, during static handgrip to fatigue (SHG) and post-exercise circulatory arrest (PECA). RESULTS The BP, HR, and MSNA responses to the CPT were similar between groups. The SBP response to SHG and PECA was similar between groups, but DBP and HR were significantly greater in HP+ women (both p < 0.05). MSNA burst frequency, but not burst incidence or total activity, tended to be elevated in HP+ women during the stressor (peak Δ from baseline 31 ± 13 vs. 23 ± 13 bursts/min; p for group = 0.06). CONCLUSION Despite no clinical signs of cardiovascular disease or hypertension, women with a history of hypertensive pregnancy display an enhanced cardiovascular reactivity to an exercise stimulus compared to women with a healthy pregnancy history. This response may be indicative of impaired cardiovascular control that precedes the clinical manifestation of hypertension or cardiovascular events.
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16
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Eckberg DL, Diedrich A, Cooke WH, Biaggioni I, Buckey JC, Pawelczyk JA, Ertl AC, Cox JF, Kuusela TA, Tahvanainen KUO, Mano T, Iwase S, Baisch FJ, Levine BD, Adams-Huet B, Robertson D, Blomqvist CG. Respiratory modulation of human autonomic function: long-term neuroplasticity in space. J Physiol 2016; 594:5629-46. [PMID: 27029027 DOI: 10.1113/jp271656] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 03/14/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS We studied healthy astronauts before, during and after the Neurolab Space Shuttle mission with controlled breathing and apnoea, to identify autonomic changes that might contribute to postflight orthostatic intolerance. Measurements included the electrocardiogram, finger photoplethysmographic arterial pressure, respiratory carbon dioxide levels, tidal volume and peroneal nerve muscle sympathetic activity. Arterial pressure fell and then rose in space, and drifted back to preflight levels after return to Earth. Vagal metrics changed in opposite directions: vagal baroreflex gain and two indices of vagal fluctuations rose and then fell in space, and descended to preflight levels upon return to Earth. Sympathetic burst frequencies (but not areas) were greater than preflight in space and on landing day, and astronauts' abilities to modulate both burst areas and frequencies during apnoea were sharply diminished. Spaceflight triggers long-term neuroplastic changes reflected by reciptocal sympathetic and vagal motoneurone responsiveness to breathing changes. ABSTRACT We studied six healthy astronauts five times, on Earth, in space on the first and 12th or 13th day of the 16 day Neurolab Space Shuttle mission, on landing day, and 5-6 days later. Astronauts followed a fixed protocol comprising controlled and random frequency breathing and apnoea, conceived to perturb their autonomic function and identify changes, if any, provoked by microgravity exposure. We recorded the electrocardiogram, finger photoplethysmographic arterial pressure, tidal carbon dioxide concentrations and volumes, and peroneal nerve muscle sympathetic activity on Earth (in the supine position) and in space. (Sympathetic nerve recordings were made during three sessions: preflight, late mission and landing day.) Arterial pressure changed systematically from preflight levels: pressure fell during early microgravity exposure, rose as microgravity exposure continued, and drifted back to preflight levels after return to Earth. Vagal metrics changed in opposite directions: vagal baroreflex gain and two indices of vagal fluctuations (root mean square of successive normal R-R intervals; and proportion of successive normal R-R intervals greater than 50 ms, divided by the total number of normal R-R intervals) rose significantly during early microgravity exposure, fell as microgravity exposure continued, and descended to preflight levels upon return to Earth. Sympathetic mechanisms also changed. Burst frequencies (but not areas) during fixed frequency breathing were greater than preflight in space and on landing day, but their control during apnoea was sharply altered: astronauts increased their burst frequencies from already high levels, but they could not modulate either burst areas or frequencies appropriately. Space travel provokes long-lasting sympathetic and vagal neuroplastic changes in healthy humans.
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Affiliation(s)
- Dwain L Eckberg
- Departments of Medicine and Physiology, Hunter Holmes McGuire Department of Veterans Affairs Medical Center, Virginia Commonwealth University School of Medicine, Richmond, VA, USA.
| | - André Diedrich
- Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, TN, USA
| | - William H Cooke
- Department of Kinesiology, Health, and Nutrition, University of Texas at San Antonio, San Antonio, TX, USA
| | - Italo Biaggioni
- Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, TN, USA
| | - Jay C Buckey
- Dartmouth Hitchcock Medical Centre, Lebanon, NH, USA
| | - James A Pawelczyk
- Department of Physiology, Pennsylvania State University, University Park and Hershey, PA, USA
| | - Andrew C Ertl
- Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, TN, USA
| | - James F Cox
- Departments of Medicine and Physiology, Hunter Holmes McGuire Department of Veterans Affairs Medical Center, Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - Tom A Kuusela
- Department of Physics, Turku University, Turku, Finland
| | - Kari U O Tahvanainen
- Department of Clinical Physiology and Nuclear Medicine, South Karelia Central Hospital, Lappeenranta, Finland
| | - Tadaaki Mano
- Gifu University of Medical Science, 795-1 Nagamine Ichihiraga, Seki, Gifu, 501-3892, Japan
| | - Satoshi Iwase
- Department of Physiology, Aichi Medical University, Aichi, Japan
| | | | - Benjamin D Levine
- Department of Medicine, University of Texas Southwestern Medical Centre at Dallas, Dallas, TX, USA.,Institute for Exercise and Environmental Medicine, Texas Health Presbyterian, Hospital, Dallas, TX, USA
| | | | - David Robertson
- Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, TN, USA
| | - C Gunnar Blomqvist
- Department of Medicine, University of Texas Southwestern Medical Centre at Dallas, Dallas, TX, USA
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17
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Florian JP, Baisch FJ, Heer M, Pawelczyk JA. Caloric restriction diminishes the pressor response to static exercise. EXTREME PHYSIOLOGY & MEDICINE 2016; 5:2. [PMID: 26793301 PMCID: PMC4719559 DOI: 10.1186/s13728-016-0043-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Accepted: 01/05/2016] [Indexed: 11/10/2022]
Abstract
BACKGROUND Astronauts in space consume fewer calories and return to earth predisposed to orthostatic intolerance. The role that caloric deficit plays in the modulation of autonomic control of the cardiovascular system is unknown. Therefore, the purpose of this study was to determine the effects of 6° head-down bedrest (an analog of spaceflight) with a hypocaloric diet (25 % caloric restriction) (CR) on autonomic neural control during static handgrip (HG) and cold pressor (CP) tests. Nine healthy young men participated in a randomized crossover bedrest (BR) study, consisting of four, two-week interventions (hypocaloric ambulatory, hypocaloric bedrest, normocaloric ambulatory, and normocaloric bedrest), each separated by 5 months. Heart rate (HR), arterial pressure, and muscle sympathetic nerve activity (MSNA) were recorded before, during, and after HG (40 % of maximum voluntary contraction to fatigue), post-exercise muscle ischemia (forearm occlusion), and CP. Bedrest and nutritional combinations were compared using two-way ANOVA with repeated measures. RESULTS HR, MSNA, and the change in systolic blood pressure during HG were attenuated with caloric restriction, but post-intervention responses for all groups were similar during post-exercise muscle ischemia. CR was associated with a higher diastolic blood pressure during CP; however, HR was directionally opposite (i.e., increase with BR, decrease with CR). CONCLUSIONS In summary 14-day caloric/fat restriction attenuated MSNA and pressor responses during isometric exercise to fatigue but not to post-exercise muscle ischemia. This indicates that the integrity of the metaboreflex is maintained whereas the influence of the mechanoreflex and/or central command may be reduced.
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Affiliation(s)
- John P Florian
- Navy Experimental Diving Unit, 321 Bullfinch Rd., Panama City, FL 32407 USA
| | | | - Martina Heer
- DLR-Institute of Aerospace Medicine, Cologne, Germany
| | - James A Pawelczyk
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802 USA
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18
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Ploutz-Snyder L. Evaluating countermeasures in spaceflight analogs. J Appl Physiol (1985) 2015; 120:915-21. [PMID: 26662054 DOI: 10.1152/japplphysiol.00860.2015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 12/02/2015] [Indexed: 11/22/2022] Open
Abstract
Countermeasures are defined as solutions to prevent the undesirable physiologic outcomes associated with spaceflight. Spaceflight analogs provide a valuable opportunity for the evaluation of countermeasures because they allow for the evaluation of more subjects, more experimental control, and are considerably less expensive than actual spaceflight. The various human analogs have differing strengths and weaknesses with respect to the development and evaluation of countermeasures. The human analogs are briefly reviewed with a focus on their suitability for countermeasure evaluation. Bed rest is the most commonly used analog for evaluating countermeasures. While countermeasures are typically developed to target one or maybe two particular physiologic issues, it is increasingly important to evaluate all of the organ systems to discern whether they might be unintended consequences on nontargeted tissues. In preparation for Mars exploration it will be necessary to fully integrate countermeasures to protect all organ systems. The synergistic and antagonistic effects of multiple countermeasures needs to be the focus of future work.
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Affiliation(s)
- Lori Ploutz-Snyder
- Exercise Physiology and Countermeasures, Universities Space Research Association, NASA Johnson Space Center, Houston, Texas
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19
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Abstract
Magnesium is an essential nutrient for muscle, cardiovascular, and bone health on Earth, and during space flight. We sought to evaluate magnesium status in 43 astronauts (34 male, 9 female; 47 ± 5 years old, mean ± SD) before, during, and after 4–6-month space missions. We also studied individuals participating in a ground analog of space flight (head-down-tilt bed rest; n = 27 (17 male, 10 female), 35 ± 7 years old). We evaluated serum concentration and 24-h urinary excretion of magnesium, along with estimates of tissue magnesium status from sublingual cells. Serum magnesium increased late in flight, while urinary magnesium excretion was higher over the course of 180-day space missions. Urinary magnesium increased during flight but decreased significantly at landing. Neither serum nor urinary magnesium changed during bed rest. For flight and bed rest, significant correlations existed between the area under the curve of serum and urinary magnesium and the change in total body bone mineral content. Tissue magnesium concentration was unchanged after flight and bed rest. Increased excretion of magnesium is likely partially from bone and partially from diet, but importantly, it does not come at the expense of muscle tissue stores. While further study is needed to better understand the implications of these findings for longer space exploration missions, magnesium homeostasis and tissue status seem well maintained during 4–6-month space missions.
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20
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Mandsager KT, Robertson D, Diedrich A. The function of the autonomic nervous system during spaceflight. Clin Auton Res 2015; 25:141-51. [PMID: 25820827 DOI: 10.1007/s10286-015-0285-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 01/08/2015] [Indexed: 11/24/2022]
Abstract
INTRODUCTION Despite decades of study, a clear understanding of autonomic nervous system activity in space remains elusive. Differential interpretation of fundamental data has driven divergent theories of sympathetic activation and vasorelaxation. METHODS This paper will review the available in-flight autonomic and hemodynamic data in an effort to resolve these discrepancies. The NASA NEUROLAB mission, the most comprehensive assessment of autonomic function in microgravity to date, will be highlighted. The mechanisms responsible for altered autonomic activity during spaceflight, which include the effects of hypovolemia, cardiovascular deconditioning, and altered central processing, will be presented. RESULTS The NEUROLAB experiments demonstrated increased sympathetic activity and impairment of vagal baroreflex function during short-duration spaceflight. Subsequent non-invasive studies of autonomic function during spaceflight have largely reinforced these findings, and provide strong evidence that sympathetic activity is increased in space relative to the supine position on Earth. Others have suggested that microgravity induces a state of relative vasorelaxation and increased vagal activity when compared to upright posture on Earth. These ostensibly disparate theories are not mutually exclusive, but rather directly reflect different pre-flight postural controls. CONCLUSION When these results are taken together, they demonstrate that the effectual autonomic challenge of spaceflight is small, and represents an orthostatic stress less than that of upright posture on Earth. In-flight countermeasures, including aerobic and resistance exercise, as well short-arm centrifugation, have been successfully deployed to counteract these mechanisms. Despite subtle changes in autonomic activity during spaceflight, underlying neurohumoral mechanisms of the autonomic nervous system remain intact and cardiovascular function remains stable during long-duration flight.
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Affiliation(s)
- Kyle Timothy Mandsager
- Division of Clinical Pharmacology, Department of Medicine, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, 1161 21st Avenue South, Suite AA3228 MCN, Nashville, TN, 37232-2195, USA
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21
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Liu J, Li Y, Verheyden B, Chen S, Chen Z, Gai Y, Liu J, Gao J, Xie Q, Yuan M, Li Q, Li L, Aubert AE. Is autonomic modulation different between European and Chinese astronauts? PLoS One 2015; 10:e0120920. [PMID: 25799561 PMCID: PMC4370477 DOI: 10.1371/journal.pone.0120920] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2014] [Accepted: 02/09/2015] [Indexed: 11/29/2022] Open
Abstract
Purpose The objective was to investigate autonomic control in groups of European and Chinese astronauts and to identify similarities and differences. Methods Beat-to-beat heart rate and finger blood pressure, brachial blood pressure, and respiratory frequency were measured from 10 astronauts (five European taking part in three different space missions and five Chinese astronauts taking part in two different space missions). Data recording was performed in the supine and standing positions at least 10 days before launch, and 1, 3, and 10 days after return. Cross-correlation analysis of heart rate and systolic pressure was used to assess cardiac baroreflex modulation. A fixed breathing protocol was performed to measure respiratory sinus arrhythmia and low-frequency power of systolic blood pressure variability. Results Although baseline cardiovascular parameters before spaceflight were similar in all astronauts in the supine position, a significant increase in sympathetic activity and a decrease in vagal modulation occurred in the European astronauts when standing; spaceflight resulted in a remarkable vagal decrease in European astronauts only. Similar baseline supine and standing values for heart rate, mean arterial pressure, and respiratory frequency were shown in both groups. Standing autonomic control was based on a balance of higher vagal and sympathetic modulation in European astronauts. Conclusion Post-spaceflight orthostatic tachycardia was observed in all European astronauts, whereas post-spaceflight orthostatic tachycardia was significantly reduced in Chinese astronauts. The basis for orthostatic intolerance is not apparent; however, many possibilities can be considered and need to be further investigated, such as genetic diversities between races, astronaut selection, training, and nutrition, etc.
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Affiliation(s)
- Jiexin Liu
- Department of Cardiology, Beijing Friendship Hospital, China Capital Medical University, Beijing, China
- Department of Cardiology, University Hospital Gasthuisberg, K. U. Leuven, Leuven, Belgium
- * E-mail: (JL); (MY)
| | | | - Bart Verheyden
- Department of Cardiology, University Hospital Gasthuisberg, K. U. Leuven, Leuven, Belgium
| | | | | | | | | | | | - Qiong Xie
- China Astronaut Center, Beijing, China
| | - Ming Yuan
- China Astronaut Center, Beijing, China
- * E-mail: (JL); (MY)
| | - Qin Li
- Department of Cardiology, Beijing Friendship Hospital, China Capital Medical University, Beijing, China
| | - Li Li
- Department of Cardiology, Beijing Friendship Hospital, China Capital Medical University, Beijing, China
| | - André E. Aubert
- Department of Cardiology, University Hospital Gasthuisberg, K. U. Leuven, Leuven, Belgium
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Hughson RL, Shoemaker JK. Autonomic responses to exercise: Deconditioning/inactivity. Auton Neurosci 2015; 188:32-5. [DOI: 10.1016/j.autneu.2014.10.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 10/13/2014] [Indexed: 12/29/2022]
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23
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Marušič U, Meeusen R, Pišot R, Kavcic V. The brain in micro- and hypergravity: the effects of changing gravity on the brain electrocortical activity. Eur J Sport Sci 2014; 14:813-22. [PMID: 24734884 DOI: 10.1080/17461391.2014.908959] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Understanding the effects of increased and decreased gravity on central nervous system is essential for developing proper physical and cognitive countermeasures to assure safe and effective space missions and human survival in space. This short review covers the available literature on the brain electrocortical activity effects of decreased and increased gravitational force comparing to the 1g Earth conditions. Among all neuroimaging methods such as functional magnetic resonance imaging (fMRI), positron-emission tomography (PET), diffusion tensor imaging (DTI), the electroencephalography (EEG) was found to be suitable method to monitor brain electrocortical activity in the extreme environments. Due to complexity and high cost of space flight missions, ground-based models have been employed to simulate microgravity effects on human body. Surprisingly, there is very limited number of publications reporting gravity-dependent EEG spectral changes. With increased gravity there are initially increased EEG activity in higher frequencies and at around 4 g appears loss of consciousness with accompanying slowing of EEG due to hypoxia. In microgravity, the most prevalent changes in EEG are faster frequencies such as alpha and beta. The results from simulated microgravity (bed rest) are pointing to changes in theta and alpha, representing signs of cortical inhibition. The changes in EEG activity in space flight are attributed to a decreased sensorimotor input while in parabolic flights short and fast transitions from hyper to microgravity presumably reflect lower arousal levels and emotional processes in microgravity. Thus, based on limited research about gravity-related changes in EEG from different environments it is difficult to draw any unequivocal conclusions. Additional systematic studies about electrocortical activity in space and parabolic flights, as well as longer bed rest studies are needed in order to advance knowledge about brain functioning in extreme conditions such as space flights.
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Affiliation(s)
- Uroš Marušič
- a Science and Research Centre, Institute for Kinesiology Research , University of Primorska , Koper , Slovenia
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Holwerda SW, Trowbridge CA, Womochel KS, Keller DM. Effects of cold modality application with static and intermittent pneumatic compression on tissue temperature and systemic cardiovascular responses. Sports Health 2014; 5:27-33. [PMID: 24381698 PMCID: PMC3548661 DOI: 10.1177/1941738112450863] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Background: In the therapeutic setting, cryotherapy with varying levels of intermittent
cyclical compression often replaces an ice bag and elastic wrap. However,
little is known about the cardiovascular strain and tissue temperature
decreases associated with cooling and intermittent compression. Hypothesis: The authors hypothesized that higher levels of intermittent compression will
result in greater reductions of tissue temperature and that all cold
modalities will cause acute increases in cardiovascular strain. Design: Experimental crossover repeated measure design. Methods: Ten healthy subjects (23 ± 3 years) volunteered for 4 cryotherapy sessions
(30-minute treatments with 30-minute passive recovery). Treatments included
ice with elastic wrap and Game Ready (GR) with no, medium (5-50 mmHg), and
high compression (5-75 mmHg). Throughout the experiment, oral, skin surface,
and intramuscular quadriceps temperatures were measured along with mean
arterial pressure, heart rate, rate pressure product, forearm blood flow,
and forearm vascular conductance. Results: Mean arterial pressure increased up to 5 minutes (P <
0.05). Forearm blood flow and forearm vascular conductance decreased after
baseline (P < 0.05), but there were no differences
between treatments. Peak intramuscular changes from baseline were −14 ± 2°C
(ice), −11 ± 6°C (GRHIGH), −10 ± 5°C (GRMED), and −7 ±
3°C (GRNO). Ice cooled the muscle the most, while GR with medium
and high compression cooled more than GR without compression
(P < 0.05). Conclusions: The application of cold and intermittent pneumatic compression using GR did
not produce acute cardiovascular strain that exceeded the strain produced by
standard ice bags/elastic wrap treatment. Greater temperature decreases are
achieved with medium- and high-pressure settings when using the GR
system. Clinical Relevance: Type of cold and amount of compression affect tissue cooling in healthy lean
subjects. All tested cold modalities caused acute increases in
cardiovascular strain; however, these increases are no more than what
healthy subjects experience with the onset of exercise.
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Carotid haemodynamics during sympathetic nervous system stimulation via handgrip and cold pressor testing in young healthy subjects: A feasibility study. Artery Res 2014. [DOI: 10.1016/j.artres.2014.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Eckberg DL, Cooke WH, Diedrich A, Levine BD, Pawelczyk JA, Buckey JC, Ertl AC, Biaggioni I, Cox JF, Robertson D, Baisch FJ, Blomqvist CG, Kuusela TA, Tahvanainen KUO. Human baroreflex rhythms persist during handgrip and muscle ischaemia. Acta Physiol (Oxf) 2013; 209:114-23. [PMID: 23809494 PMCID: PMC3875341 DOI: 10.1111/apha.12143] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Revised: 05/20/2013] [Accepted: 06/20/2013] [Indexed: 12/20/2022]
Abstract
AIM To determine whether physiological, rhythmic fluctuations of vagal baroreflex gain persist during exercise, post-exercise ischaemia and recovery. METHODS We studied responses of six supine healthy men and one woman to a stereotyped protocol comprising rest, handgrip exercise at 40% maximum capacity to exhaustion, post-exercise forearm ischaemia and recovery. We measured electrocardiographic R-R intervals, photoplethysmographic finger arterial pressures and peroneal nerve muscle sympathetic activity. We derived vagal baroreflex gains from a sliding (25-s window moved by 2-s steps) systolic pressure-R-R interval transfer function at 0.04-0.15 Hz. RESULTS Vagal baroreflex gain oscillated at low, nearly constant frequencies throughout the protocol (at approx. 0.06 Hz - a period of about 18 s); however, during exercise, most oscillations were at low-gain levels, and during ischaemia and recovery, most oscillations were at high-gain levels. CONCLUSIONS Vagal baroreflex rhythms are not abolished by exercise, and they are not overwhelmed after exercise during ischaemia and recovery.
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Affiliation(s)
- D. L. Eckberg
- Departments of Medicine and Physiology, Hunter Holmes McGuire Department of Veterans Affairs Medical Center and Medical College of Virginia at Virginia Commonwealth University, Richmond, VA, USA
| | - W. H. Cooke
- Health and Kinesiology, University of Texas at San Antonio, San Antonio, TX, USA
| | - A. Diedrich
- Division of Clinical Pharmacology, Department of Medicine, Autonomic Dysfunction Center, Vanderbilt University, Nashville, TN, USA
| | - B. D. Levine
- Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA
| | - J. A. Pawelczyk
- The Pennsylvania State University, University Park and Hershey, PA, USA
| | - J. C. Buckey
- Dartmouth Hitchcock Medical Center, Lebanon, NH, USA
| | - A. C. Ertl
- Division of Clinical Pharmacology, Department of Medicine, Autonomic Dysfunction Center, Vanderbilt University, Nashville, TN, USA
| | - I. Biaggioni
- Division of Clinical Pharmacology, Department of Medicine, Autonomic Dysfunction Center, Vanderbilt University, Nashville, TN, USA
| | - J. F. Cox
- Departments of Medicine and Physiology, Hunter Holmes McGuire Department of Veterans Affairs Medical Center and Medical College of Virginia at Virginia Commonwealth University, Richmond, VA, USA
| | - D. Robertson
- Division of Clinical Pharmacology, Department of Medicine, Autonomic Dysfunction Center, Vanderbilt University, Nashville, TN, USA
| | - F. J. Baisch
- DLR-Institute for Aerospace Medicine, Cologne, Germany
| | - C. G. Blomqvist
- Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA
| | - T. A. Kuusela
- Department of Physics, Turku University, Turku, Finland
| | - K. U. O. Tahvanainen
- Department of Clinical Physiology and Nuclear Medicine, South Karelia Central Hospital, Lappeenranta, Finland
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Florian JP, Simmons EE, Chon KH, Faes L, Shykoff BE. Cardiovascular and autonomic responses to physiological stressors before and after six hours of water immersion. J Appl Physiol (1985) 2013; 115:1275-89. [PMID: 23950166 DOI: 10.1152/japplphysiol.00466.2013] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The physiological responses to water immersion (WI) are known; however, the responses to stress following WI are poorly characterized. Ten healthy men were exposed to three physiological stressors before and after a 6-h resting WI (32-33°C): 1) a 2-min cold pressor test, 2) a static handgrip test to fatigue at 40% of maximum strength followed by postexercise muscle ischemia in the exercising forearm, and 3) a 15-min 70° head-up-tilt (HUT) test. Heart rate (HR), systolic and diastolic blood pressure (SBP and DBP), cardiac output (Q), limb blood flow (BF), stroke volume (SV), systemic and calf or forearm vascular resistance (SVR and CVR or FVR), baroreflex sensitivity (BRS), and HR variability (HRV) frequency-domain variables [low-frequency (LF), high-frequency (HF), and normalized (n)] were measured. Cold pressor test showed lower HR, SBP, SV, Q, calf BF, LFnHRV, and LF/HFHRV and higher CVR and HFnHRV after than before WI (P < 0.05). Handgrip test showed no effect of WI on maximum strength and endurance and lower HR, SBP, SV, Q, and calf BF and higher SVR and CVR after than before WI (P < 0.05). During postexercise muscle ischemia, HFnHRV increased from baseline after WI only, and LFnHRV was lower after than before WI (P < 0.05). HUT test showed lower SBP, DBP, SV, forearm BF, and BRS and higher HR, FVR, LF/HFHRV, and LFnHRV after than before WI (P < 0.05). The changes suggest differential activation/depression during cold pressor and handgrip (reduced sympathetic/elevated parasympathetic) and HUT (elevated sympathetic/reduced parasympathetic) following 6 h of WI.
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Zhang LF. Region-specific vascular remodeling and its prevention by artificial gravity in weightless environment. Eur J Appl Physiol 2013; 113:2873-95. [DOI: 10.1007/s00421-013-2597-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2012] [Accepted: 01/20/2013] [Indexed: 10/27/2022]
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Mars 520-d mission simulation reveals protracted crew hypokinesis and alterations of sleep duration and timing. Proc Natl Acad Sci U S A 2013; 110:2635-40. [PMID: 23297197 DOI: 10.1073/pnas.1212646110] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The success of interplanetary human spaceflight will depend on many factors, including the behavioral activity levels, sleep, and circadian timing of crews exposed to prolonged microgravity and confinement. To address the effects of the latter, we used a high-fidelity ground simulation of a Mars mission to objectively track sleep-wake dynamics in a multinational crew of six during 520 d of confined isolation. Measurements included continuous recordings of wrist actigraphy and light exposure (4.396 million min) and weekly computer-based neurobehavioral assessments (n = 888) to identify changes in the crew's activity levels, sleep quantity and quality, sleep-wake periodicity, vigilance performance, and workload throughout the record-long 17 mo of mission confinement. Actigraphy revealed that crew sedentariness increased across the mission as evident in decreased waking movement (i.e., hypokinesis) and increased sleep and rest times. Light exposure decreased during the mission. The majority of crewmembers also experienced one or more disturbances of sleep quality, vigilance deficits, or altered sleep-wake periodicity and timing, suggesting inadequate circadian entrainment. The results point to the need to identify markers of differential vulnerability to hypokinesis and sleep-wake changes during the prolonged isolation of exploration spaceflight and the need to ensure maintenance of circadian entrainment, sleep quantity and quality, and optimal activity levels during exploration missions. Therefore, successful adaptation to such missions will require crew to transit in spacecraft and live in surface habitats that instantiate aspects of Earth's geophysical signals (appropriately timed light exposure, food intake, exercise) required for temporal organization and maintenance of human behavior.
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Cerebrovascular autoregulation: lessons learned from spaceflight research. Eur J Appl Physiol 2012; 113:1909-17. [PMID: 23132388 DOI: 10.1007/s00421-012-2539-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Accepted: 10/24/2012] [Indexed: 10/27/2022]
Abstract
This review summarizes our current understanding of cerebral blood flow regulation with exposure to microgravity, outlines potential mechanisms associated with post-flight orthostatic intolerance, and proposes future directions for research and linkages with cerebrovascular disorders found in the general population. It encompasses research from cellular mechanisms (e.g. hind limb suspension: tissue, animal studies) to whole body analysis with respect to understanding human responses using space analogue studies (bed rest, parabolic flight) as well as data collected before, during, and after spaceflight. Recent evidence indicates that cerebrovascular autoregulation may be impaired in some astronauts leading to increased susceptibility to syncope upon return to a gravitational environment. The proposed review not only provides insights into the mechanisms of post-flight orthostatic intolerance, but also increases our understanding of the mechanisms associated with pathophysiological conditions (e.g. unexplained syncope) with clinical applications in relation to postural hypotension or intradialytic hypotension.
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Goswami N, Batzel JJ, Clément G, Stein TP, Hargens AR, Sharp MK, Blaber AP, Roma PG, Hinghofer-Szalkay HG. Maximizing information from space data resources: a case for expanding integration across research disciplines. Eur J Appl Physiol 2012; 113:1645-54. [PMID: 23073848 DOI: 10.1007/s00421-012-2507-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2012] [Accepted: 09/20/2012] [Indexed: 11/30/2022]
Abstract
Regulatory systems are affected in space by exposure to weightlessness, high-energy radiation or other spaceflight-induced changes. The impact of spaceflight occurs across multiple scales and systems. Exploring such interactions and interdependencies via an integrative approach provides new opportunities for elucidating these complex responses. This paper argues the case for increased emphasis on integration, systematically archiving, and the coordination of past, present and future space and ground-based analogue experiments. We also discuss possible mechanisms for such integration across disciplines and missions. This article then introduces several discipline-specific reviews that show how such integration can be implemented. Areas explored include: adaptation of the central nervous system to space; cerebral autoregulation and weightlessness; modelling of the cardiovascular system in space exploration; human metabolic response to spaceflight; and exercise, artificial gravity, and physiologic countermeasures for spaceflight. In summary, spaceflight physiology research needs a conceptual framework that extends problem solving beyond disciplinary barriers. Administrative commitment and a high degree of cooperation among investigators are needed to further such a process. Well-designed interdisciplinary research can expand opportunities for broad interpretation of results across multiple physiological systems, which may have applications on Earth.
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Affiliation(s)
- Nandu Goswami
- Institute of Physiology, Medical University of Graz, Harrachgasse 21, Graz 8010, Austria.
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Weiner RB, Weyman AE, Kim JH, Wang TJ, Picard MH, Baggish AL. The impact of isometric handgrip testing on left ventricular twist mechanics. J Physiol 2012; 590:5141-50. [PMID: 22890704 DOI: 10.1113/jphysiol.2012.236166] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Left ventricular (LV) rotation occurs due to contraction of obliquely oriented myocardial fibres. Left ventricular twist (LVT) results from rotation of the apex and base in opposite directions. Although LVT is altered in various cardiac diseases, physiological factors that affect LVT remain incompletely understood. Isometric handgrip testing (IHGT), a well-established laboratory-based technique to increase LV afterload, was performed for 3 min at 40% maximum force generation in healthy human subjects (n = 18, mean age 29.7 ± 2.7 years). Speckle-tracking echocardiography was used to measure LV volumes, LV apical and basal rotation, peak systolic LVT and peak early diastolic untwisting rate (UTR) at rest and at peak IHGT. IHGT led to significant increase in systemic blood pressure (systolic, 120.6 ± 9.7 vs. 155.6 ± 14.5 mmHg, P < 0.001; diastolic, 67.5 ± 6.4 vs. 94.1 ± 21.1 mmHg, P < 0.001) and LV end-systolic volume (44.2 ± 7.8 vs. 50.5 ± 10.8 ml, P = 0.005), as well as a significant increase in heart rate (62.8 ± 11.7 vs. 84.7 ± 13.8 beats min−1; P < 0.001). IHGT produced a significant acute reduction in LV stroke volume (63.9 ± 12.0 vs. 49.4 ± 7.8 ml, P < 0.001). In this setting, there was a significant decrease in peak systolic apical rotation (11.9 ± 3.0 vs. 8.6 ± 2.2 deg, P < 0.001) and a resultant 25% decrease in peak systolic LVT (16.6 ± 2.8 vs. 12.5 ± 2.8 deg, P < 0.001). The magnitude of peak early diastolic UTR did not change (−114.5 ± 26.4 vs. −110.6 ± 39.8 deg s−1, P = 0.71). Peak systolic apical rotation and LVT decrease during IHGT in healthy humans. This impairment of LV twist mechanics may in part underlie the LV dysfunction that can occur in the clinical context of acute increase in afterload.
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Affiliation(s)
- Rory B Weiner
- Cardiovascular Performance Program, Massachusetts General Hospital, Yawkey Suite 5B, 55 Fruit Street, Boston, MA 02114, USA.
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Neves VR, Kiviniemi AM, Hautala AJ, Karjalainen J, Piira OP, Catai AM, Mäkikallio TH, Huikuri HV, Tulppo MP. Heart Rate Dynamics after Exercise in Cardiac Patients with and without Type 2 Diabetes. Front Physiol 2011; 2:57. [PMID: 21922009 PMCID: PMC3166711 DOI: 10.3389/fphys.2011.00057] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Accepted: 08/18/2011] [Indexed: 11/25/2022] Open
Abstract
Purpose: The incidence of cardiovascular events is higher in coronary artery disease patients with type 2 diabetes (CAD + T2D) than in CAD patients without T2D. There is increasing evidence that the recovery phase after exercise is a vulnerable phase for various cardiovascular events. We hypothesized that autonomic regulation differs in CAD patients with and without T2D during post-exercise condition. Methods: A symptom-limited maximal exercise test on a bicycle ergometer was performed for 68 CAD + T2D patients (age 61 ± 5 years, 78% males, ejection fraction (EF) 67 ± 8, 100% on β-blockade), and 64 CAD patients (age 62 ± 5 years, 80% males, EF 64 ± 8, 100% on β-blockade). Heart rate (HR) recovery after exercise was calculated as the slope of HR during the first 60 s after cessation of exercise (HRRslope). R–R intervals were measured before (5 min) and after exercise from 3 to 8 min, both in a supine position. R–R intervals were analyzed using time and frequency methods and a detrended fluctuation method (α1). Results: BMI was 30 ± 4 vs. 27 ± 3 kg m2 (p < 0.001); maximal exercise capacity, 6.5 ± 1.7 vs. 7.7 ± 1.9 METs (p < 0.001); maximal HR, 128 ± 19 vs. 132 ± 18 bpm (p = ns); and HRRslope, −0.53 ± 0.17 vs. −0.62 ± 0.15 beats/s (p = 0.004), for CAD patients with and without T2D, respectively. There was no differences between the groups in HRRslope after adjustment for METs, BMI, and medication (ANCOVA, p = 0.228 for T2D and, e.g., p = 0.030 for METs). CAD + T2D patients had a higher HR at rest than non-diabetic patients (57 ± 10 vs. 54 ± 6 bpm, p = 0.030), but no other differences were observed in HR dynamics at rest or in post-exercise condition. Conclusion: HR recovery is delayed in CAD + T2D patients, suggesting impairment of vagal activity and/or augmented sympathetic activity after exercise. Blunted HR recovery after exercise in diabetic patients compared with non-diabetic patients is more closely related to low exercise capacity and obesity than to T2D itself.
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Affiliation(s)
- Victor R Neves
- Department of Exercise and Medical Physiology Verve, Oulu, Finland
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Mano T, Nishimura N, Iwase S. Sympathetic neural influence on bone metabolism in microgravity (Review). ACTA ACUST UNITED AC 2011; 97:354-61. [PMID: 21138811 DOI: 10.1556/aphysiol.97.2010.4.8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Bone loss is one of the most important complications for astronauts who are exposed to long-term microgravity in space and also for bedridden elderly people. Recent studies have indicated that the sympathetic nervous system plays a role in bone metabolism. This paper reviews findings concerning with sympathetic influences on bone metabolism to hypothesize the mechanism how sympathetic neural functions are related to bone loss in microgravity. Animal studies have suggested that leptin stimulates hypothalamus increasing sympathetic outflow to bone and enhances bone resorption through noradrenaline and β-adrenoreceptors in bone. In humans, even though there have been some controversial findings, use of β-adrenoblockers has been reported to be beneficial for prevention of osteoporosis and bone fracture. On the other hand, microneurographically-recorded sympathetic nerve activity was enhanced by exposure to microgravity in space as well as dry immersion or long-term bed rest to simulate microgravity. The same sympathetic activity became higher in elderly people whose bone mass becomes generally reduced. Our recent findings indicated a significant correlation between muscle sympathetic nerve activity and urinary deoxypyridinoline as a specific marker measuring bone resorption. Based on these findings we would like to propose a following hypothesis concerning the sympathetic involvement in the mechanism of bone loss in microgravity: An exposure to prolonged microgravity may enhance sympathetic neural traffic not only to muscle but also to bone. This sympathetic enhancement increases plasma noradrenaline level and inhibits osteogenesis and facilitates bone resorption through β-adrenoreceptors in bone to facilitate bone resorption to reduce bone mass. The use of β-adrenoblockers to prevent bone loss in microgravity may be reasonable.
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Affiliation(s)
- Tadaaki Mano
- Gifu University of Medical Science Seki, Gifu 501-3892 Japan.
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35
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Casey DP, Curry TB, Joyner MJ, Charkoudian N, Hart EC. Relationship between muscle sympathetic nerve activity and aortic wave reflection characteristics in young men and women. Hypertension 2011; 57:421-7. [PMID: 21242459 DOI: 10.1161/hypertensionaha.110.164517] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Increased arterial stiffness is associated with higher levels of aortic wave reflection and aortic blood pressure. Recent evidence suggests a link between muscle sympathetic nerve activity and indices of arterial stiffness. Therefore, the aims of this study were to examine the relationship between resting muscle sympathetic nerve activity and characteristics of aortic pressure wave reflection and the influence of sex on these relationships. In 44 subjects (23 females and 21 males; 25 ± 1 years of age), we measured muscle sympathetic nerve activity via peroneal microneurography. In addition, noninvasive aortic pressure waveforms were synthesized from radial pressure waveforms obtained from applanation tonometry. Aortic blood pressure, augmentation index, wave reflection amplitude, and wasted left ventricular energy were calculated. Resting sympathetic activity (bursts/100 heart beats) was not associated with any of the aortic pressure wave reflection characteristics for all patients. However, there was a positive relationship between sympathetic activity and augmentation index (r = 0.46; P = 0.05) in men. Further, sympathetic activity in men was related to wave reflection amplitude (r = 0.53; P<0.05) and wasted left ventricular energy (r = 0.57; P<0.01). In contrast to men, women demonstrated strong inverse relationships between sympathetic activity and augmentation index (r = -0.63), wave reflection amplitude ( r = -0.59), and wasted left ventricular energy (r = -0.58; P<0.01 for all). Our results suggest another possible mechanism by which young women are protected against the development of cardiovascular disease.
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Affiliation(s)
- Darren P Casey
- Department of Anesthesiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA.
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Navasiolava NM, Custaud MA, Tomilovskaya ES, Larina IM, Mano T, Gauquelin-Koch G, Gharib C, Kozlovskaya IB. Long-term dry immersion: review and prospects. Eur J Appl Physiol 2010; 111:1235-60. [PMID: 21161267 DOI: 10.1007/s00421-010-1750-x] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2010] [Indexed: 11/29/2022]
Abstract
Dry immersion, which is a ground-based model of prolonged conditions of microgravity, is widely used in Russia but is less well known elsewhere. Dry immersion involves immersing the subject in thermoneutral water covered with an elastic waterproof fabric. As a result, the immersed subject, who is freely suspended in the water mass, remains dry. For a relatively short duration, the model can faithfully reproduce most physiological effects of actual microgravity, including centralization of body fluids, support unloading, and hypokinesia. Unlike bed rest, dry immersion provides a unique opportunity to study the physiological effects of the lack of a supporting structure for the body (a phenomenon we call 'supportlessness'). In this review, we attempt to provide a detailed description of dry immersion. The main sections of the paper discuss the changes induced by long-term dry immersion in the neuromuscular and sensorimotor systems, fluid-electrolyte regulation, the cardiovascular system, metabolism, blood and immunity, respiration, and thermoregulation. The long-term effects of dry immersion are compared with those of bed rest and actual space flight. The actual and potential uses of dry immersion are discussed in the context of fundamental studies and applications for medical support during space flight and terrestrial health care.
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Abstract
Convincing evidence has accumulated of regulation of bone by the central nervous system. The neural connection between brain and bone is mediated centrally by classic neurotransmitters and several neuropeptides, and peripherally by many of the same neurotransmitters and neuropeptides, albeit with actions opposite to their central effects. Pharmacologic blockade of ß2-adrenergic receptors or disruption of the gene encoding them increases bone mass, whereas increased activity of the sympathetic nervous system (SNS) contributes to bone loss. Brainstem serotonergic neurons regulate SNS activity and its modulation by leptin. Physiologic stimulation of osteoblastic nicotinic receptors results in proliferation and deposition of bone, whereas higher levels inhibit osteoblast function. Activation of sensory nerves has a centrally mediated action on bone, albeit poorly understood. The relative importance of, and interactions between autonomic, sensory, and peripheral nervous system actions on bone mass are also not clear in healthy individuals, and less so in pathologic states.
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Affiliation(s)
- Weiping Qin
- Center of Excellence for the Medical Consequences of Spinal Cord Injury, Bronx, NY 10468, USA.
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38
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Verheyden B, Liu J, Beckers F, Aubert AE. Operational point of neural cardiovascular regulation in humans up to 6 months in space. J Appl Physiol (1985) 2010; 108:646-54. [DOI: 10.1152/japplphysiol.00883.2009] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Entering weightlessness affects central circulation in humans by enhancing venous return and cardiac output. We tested whether the operational point of neural cardiovascular regulation in space sets accordingly to adopt a level close to that found in the ground-based horizontal position. Heart rate (HR), finger blood and brachial blood pressure (BP), and respiratory frequency were collected in 11 astronauts from nine space missions. Recordings were made in supine and standing positions at least 10 days before launch and during spaceflight ( days 5– 19, 45– 67, 77– 116, 146– 180). Cross-correlation analyses of HR and systolic BP were used to measure three complementary aspects of cardiac baroreflex modulation: 1) baroreflex sensitivity, 2) number of effective baroreflex estimates, and 3) baroreflex time delay. A fixed breathing protocol was performed to measure respiratory sinus arrhythmia and low-frequency power of systolic BP variability. We found that HR and mean arterial pressure did not differ from preflight supine values for up to 6 mo in space. Respiration frequency tended to decrease during prolonged spaceflight. Concerning neural markers of cardiovascular regulation, we observed in-flight adaptations toward homeostatic conditions similar to those found in the ground-based supine position. Surprisingly, this was not the case for baroreflex time delay distribution, which had somewhat longer latencies in space. Except for this finding, our results confirm that the operational point of neural cardiovascular regulation in space sets to a level close to that of an Earth-based supine position. This adaptation level suggests that circulation is chronically relaxed for at least 6 mo in space.
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Affiliation(s)
- B. Verheyden
- Laboratory Experimental Cardiology and Interdisciplinary Centre for Space Studies, University Hospital Gasthuisberg, Leuven, Belgium
| | - J. Liu
- Laboratory Experimental Cardiology and Interdisciplinary Centre for Space Studies, University Hospital Gasthuisberg, Leuven, Belgium
| | - F. Beckers
- Laboratory Experimental Cardiology and Interdisciplinary Centre for Space Studies, University Hospital Gasthuisberg, Leuven, Belgium
| | - A. E. Aubert
- Laboratory Experimental Cardiology and Interdisciplinary Centre for Space Studies, University Hospital Gasthuisberg, Leuven, Belgium
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Eckberg DL, Halliwill JR, Beightol LA, Brown TE, Taylor JA, Goble R. Human vagal baroreflex mechanisms in space. J Physiol 2010; 588:1129-38. [PMID: 20156846 DOI: 10.1113/jphysiol.2009.186650] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Although astronauts' cardiovascular function is normal while they are in space, many have altered haemodynamic responses to standing after they return to Earth, including inordinate tachycardia, orthostatic hypotension, and uncommonly, syncope. Simulated microgravity impairs vagal baroreceptor-cardiac reflex function and causes orthostatic hypotension. Actual microgravity, however, has been shown to either increase, or not change vagal baroreflex gain. In this study, we tested the null hypothesis that spaceflight does not impair human baroreflex mechanisms. We studied 11 American and two German astronauts before, during (flight days 2-8), and after two, 9- and 10-day space shuttle missions, with graded neck pressure and suction, to elicit sigmoid, vagally mediated carotid baroreflex R-R interval responses. Baseline systolic pressures tended to be higher in space than on Earth (P = 0.015, repeated measures analysis of variance), and baseline R-R intervals tended to be lower (P = 0.049). Baroreceptor-cardiac reflex relations were displaced downward on the R-R interval axis in space. The average range of R-R interval responses to neck pressure changes declined from preflight levels by 37% on flight day 8 (P = 0.051), maximum R-R intervals declined by 14% (P = 0.003), and vagal baroreflex gain by 9% (P = 0.009). These measures returned to preflight levels by 7-10 days after astronauts returned to Earth. This study documents significant increases of arterial pressure and impairment of vagal baroreflex function in space. These results and results published earlier indicate that microgravity exposure augments sympathetic, and diminishes vagal cardiovascular influences.
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Affiliation(s)
- Dwain L Eckberg
- Department of Medicine, Hunter Holmes McGuire Department of Veterans Affairs Medical Center and Medical College of Virginia at Virginia Commonwealth University, Richmond, VA, USA.
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Aubert AE, Verheyden B, d′Ydewalle C, Beckers F, Van den Bergh O. Effects of mental stress on autonomic cardiac modulation during weightlessness. Am J Physiol Heart Circ Physiol 2010; 298:H202-9. [DOI: 10.1152/ajpheart.00865.2009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sustained weightlessness affects all body functions, among these also cardiac autonomic control mechanisms. How this may influence neural response to central stimulation by a mental arithmetic task remains an open question. The hypothesis was tested that microgravity alters cardiovascular neural response to standardized cognitive load stimuli. Beat-to-beat heart rate, brachial blood pressure, and respiratory frequency were collected in five astronauts, taking part in three different short-duration (10 to 11 days) space missions to the International Space Station. Data recording was performed in supine position 1 mo before launch; at days 5 or 8 in space; and on days 1, 4, and 25 after landing. Heart rate variability (HRV) parameters were obtained in the frequency domain. Measurements were performed in the control condition for 10 min and during a 5-min mental arithmetic stress task, consisting of deducting 17 from a four-digit number, read by a colleague, and orally announcing the result. Our results show that over all sessions (pre-, in-, and postflight), mental stress induced an average increase in mean heart rate (Δ7 ± 1 beats/min; P = 0.03) and mean arterial pressure (Δ7 ± 1 mmHg; P = 0.006). A sympathetic excitation during mental stress was shown from HRV parameters: increase of low frequency expressed in normalized units (Δ8.3 ± 1.4; P = 0.004) and low frequency/high frequency (Δ1.6 ± 0.3; P = 0.001) and decrease of high frequency expressed in normalized units (Δ8.9 ± 1.4; P = 0.004). The total power was not influenced by mental stress. No effect of spaceflight was found on baseline heart rate, mean arterial pressure, and HRV parameters. No differences in response to mental stress were found between pre-, in-, and postflight. Our findings confirm that a mental arithmetic task in astronauts elicits sympathovagal shifts toward enhanced sympathetic modulation and reduced vagal modulation. However, these responses are not changed in space during microgravity or after spaceflight.
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Affiliation(s)
- André E. Aubert
- Laboratory of Experimental Cardiology, and Interdisciplinary Centre for Space Studies, University Hospital Gasthuisberg; and
| | - Bart Verheyden
- Laboratory of Experimental Cardiology, and Interdisciplinary Centre for Space Studies, University Hospital Gasthuisberg; and
| | | | - Frank Beckers
- Laboratory of Experimental Cardiology, and Interdisciplinary Centre for Space Studies, University Hospital Gasthuisberg; and
| | - Omer Van den Bergh
- Research Group on Health Psychology, Katholieke Universiteit Leuven, Leuven, Belgium
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41
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Law LAF, Avin KG. Endurance time is joint-specific: a modelling and meta-analysis investigation. ERGONOMICS 2010; 53:109-29. [PMID: 20069487 PMCID: PMC2891087 DOI: 10.1080/00140130903389068] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Static task intensity-endurance time (ET) relationships (e.g. Rohmert's curve) were first reported decades ago. However, a comprehensive meta-analysis to compare experimentally-observed ETs across bodily regions has not been reported. We performed a systematic literature review of ETs for static contractions, developed joint-specific power and exponential models of the intensity-ET relationships, and compared these models between each joint (ankle, trunk, hand/grip, elbow, knee, and shoulder) and the pooled data (generalised curve). 194 publications were found, representing a total of 369 data points. The power model provided the best fit to the experimental data. Significant intensity-dependent ET differences were predicted between each pair of joints. Overall, the ankle was most fatigue-resistant, followed by the trunk, hand/grip, elbow, knee and finally the shoulder was most fatigable. We conclude ET varies systematically between joints, in some cases with large effect sizes. Thus, a single generalised ET model does not adequately represent fatigue across joints. STATEMENT OF RELEVANCE: Rohmert curves have been used in ergonomic analyses of fatigue, as there are limited tools available to accurately predict force decrements. This study provides updated endurance time-intensity curves using a large meta-analysis of fatigue data. Specific models derived for five distinct joint regions should further increase prediction accuracy.
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42
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Karlsson LL, Montmerle S, Rohdin M, Linnarsson D. Central command and metaboreflex cardiovascular responses to sustained handgrip during microgravity. Respir Physiol Neurobiol 2009; 169 Suppl 1:S46-9. [DOI: 10.1016/j.resp.2009.04.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Revised: 03/26/2009] [Accepted: 04/14/2009] [Indexed: 10/20/2022]
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Pagani M, Pizzinelli P, Beltrami S, Massaro M, Lucini D, Iellamo F. Baroreflex and metaboreflex control of cardiovascular system during exercise in space. Respir Physiol Neurobiol 2009; 169 Suppl 1:S42-5. [PMID: 19446046 DOI: 10.1016/j.resp.2009.05.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Revised: 05/02/2009] [Accepted: 05/04/2009] [Indexed: 11/29/2022]
Abstract
This brief review summarizes current knowledge on the neural mechanisms of cardiovascular regulation during exercise in space, with specific emphasis on the role of the arterial baroreflex and the muscle metaboreflex, with the attendant modifications in autonomic nervous system activity, in determining the cardiovascular responses to exercise in microgravity conditions. Available data suggest that the muscle metaboreflex is enhanced during dynamic exercise in space and that the potentiation of the muscle metaboreflex affects the vagally mediated arterial baroreflex contribution to HR control.
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Affiliation(s)
- Massimo Pagani
- UO Telematica per la Medicina e Medicina dello Sport, Ospedale "L. Sacco", Università degli Studi, Milano, Italy.
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KURIMOTO F, SAITO K, WATANABE T, NAGATANI T, NISHIWAKI K, WAKABAYASHI T, IWASE S. Preliminary Measurement of Intraoperative Sympathetic Nerve Activity Using Microneurography and Laser Doppler Flowmetry During Surgical Resection of Suprasellar Tumors. Neurol Med Chir (Tokyo) 2009; 49:13-21. [DOI: 10.2176/nmc.49.13] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
| | - Kiyoshi SAITO
- Department of Neurosurgery, Nagoya University Graduate School of Medicine
| | | | - Tetsuya NAGATANI
- Department of Neurosurgery, Nagoya University Graduate School of Medicine
| | | | | | - Satoshi IWASE
- Department of Autonomic Neuroscience, Aichi Medical University
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Capelli C, Antonutto G, Cautero M, Tam E, Ferretti G. Metabolic and cardiovascular responses during sub-maximal exercise in humans after 14 days of head-down tilt bed rest and inactivity. Eur J Appl Physiol 2008; 104:909-18. [DOI: 10.1007/s00421-008-0848-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/25/2008] [Indexed: 11/28/2022]
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46
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Beat-to-beat agreement of noninvasive tonometric and intra-radial arterial blood pressure during microgravity and hypergravity generated by parabolic flights. Blood Press Monit 2007; 12:357-62. [DOI: 10.1097/01.mbp.0000209088.78235.59] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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47
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Marenzana M, De Souza RL, Chenu C. Blockade of beta-adrenergic signaling does not influence the bone mechano-adaptive response in mice. Bone 2007; 41:206-15. [PMID: 17543595 DOI: 10.1016/j.bone.2007.04.184] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Revised: 03/02/2007] [Accepted: 04/14/2007] [Indexed: 11/23/2022]
Abstract
The involvement of the sympathetic nervous system (SNS) in the modulation of bone adaptation to its load-bearing demand remains controversial. This study tested the involvement of SNS in the adaptive response of trabecular and cortical bone to either external loading or disuse. External loading consisted of cyclic strain (40 cycles, peak 1500 microstrain) applied for 7 min, 3 days/week, while disuse was induced by unilateral sciatic neurectomy (SN). C57Bl/J6 mice, female, 9 weeks old, were subjected to loading or disuse for 2 weeks. Half of the loaded and SN mice were injected with the beta-adrenergic antagonist, propranolol (PRO, 20 mug/g) 1 week before the start of loading or disuse and during all the duration of the experiment. MicroCT analysis of the tibiae showed that the applied load induced significant changes on both trabecular architecture and cortical geometry compared to the contralateral controls, indicating increased bone mass. In contrast, disuse markedly reduced trabecular and cortical indexes. However, these adaptive responses were not altered by PRO treatment. We further tested whether the lack of protective effect of PRO against disuse-induced bone loss was due to the very short duration of treatment by blocking SNS signaling for 8 weeks with either PRO (0.5 mg/ml in drinking water) or guanethidine sulfate (GS, 40 mug/g, injected). At the end of fourth week of treatment, mice underwent SN surgery so that disuse was induced for the remaining 4 weeks. Again, neither PRO nor GS treatments altered the disuse-induced bone loss in the neurectomized tibia. In addition, blockade of SNS signaling for either 3 or 8 weeks did not affect the basal trabecular bone architecture in control tibiae and in L4 vertebrae. This study shows that the mechano-adaptive response occurring in trabecular and cortical bone upon loading or disuse is not altered by inactivation of beta-adrenergic signaling. Furthermore, sympathectomy had no effect on trabecular bone at different skeletal sites. This suggests that the osteo-regulatory action of beta-adrenergic signaling is not involved in the bone mechano-adaptive response and must therefore affect other bone regulatory pathways.
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Affiliation(s)
- Massimo Marenzana
- Department of Veterinary Basic Sciences, The Royal Veterinary College, Royal College Street, London, United Kingdom.
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Low DA, Vu A, Brown M, Davis SL, Keller DM, Levine BD, Crandall CG. Temporal Thermometry Fails to Track Body Core Temperature during Heat Stress. Med Sci Sports Exerc 2007; 39:1029-35. [PMID: 17596768 DOI: 10.1249/mss.0b013e318050ca3e] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE The aim of this study was to assess the accuracy of temporal scanning thermometry in monitoring internal temperature increases during passive heating. METHODS Sixteen subjects (5 males and 11 females) underwent a whole-body passive heat stress (water-perfused suit) to increase internal temperature. Temperatures were obtained with a temporal scanner and with an ingestible-pill telemetry system that tracks intestinal temperature. Temperatures were recorded while subjects were normothermic (34 degrees C water-perfusing suit) and every 10 min during passive heating (48 degrees C water-perfusing suit). RESULTS Heart rate (ECG), mean skin temperature (weighted six-site average), skin blood flow (laser Doppler flowmetry), and sweat rate (capacitance hygrometry) were all significantly elevated at the end of heating (all P < 0.001). Pre-heat stress temporal-derived temperature was not different from intestinal temperature (36.98 +/- 0.09 vs 37.01 +/- 0.09 degrees C, respectively, P = 0.76). However, after 30 min of heating (the greatest duration of heating completed by all subjects), temporal-derived temperature decreased to below the pre-heat stress baseline (-0.22 +/- 0.11), whereas intestinal temperature increased by 0.39 +/- 0.07 degrees C (P < 0.001 between the two methods). After 50 min of heating (N = 11), intestinal-derived internal temperature increased by 0.70 +/- 0.09 degrees C, whereas temporal-derived temperature decreased by 0.29 +/- 0.10 degrees C (P < 0.001). The group average (+/- SEM) R2 and slope between the two methods were 0.29 +/- 0.08 and -0.34 +/- 0.14, respectively. CONCLUSION These results demonstrate that temporal scanning does not track internal temperature, as measured via intestinal temperature, during passive heating. Given these findings, it is recommended that this technique not be used to assess temperature in hyperthermic diaphoretic subjects.
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Affiliation(s)
- David A Low
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas, TX 75231, USA
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49
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Mourot L, Cluzeau C, Regnard J. [Physiological assessment of a gaseous cryotherapy device: thermal effects and changes in cardiovascular autonomic control]. ACTA ACUST UNITED AC 2007; 50:209-17. [PMID: 17300850 DOI: 10.1016/j.annrmp.2007.01.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2006] [Accepted: 01/03/2007] [Indexed: 12/11/2022]
Abstract
PURPOSE The aim of the study was to assess thermal effects and cardiovascular autonomic control with application of a gaseous cryotherapy device to the hand. MATERIAL AND METHODS Before, during and after cooling of the left hand, we continuously evaluated cutaneous temperature of the right and left hands, as well as heart rate (HR) and arterial blood pressure (BP) and their neurovegetatif control (HR and BP variability) in 8 healthy subjects. Comparison of cooling caused by projection of CO(2) microcrystals (2 min) under high pressure (75 bar) and low temperature (-78 degrees C) to that with application of a latex ice pack (15 min). Assessment of whether cooling triggered any changes in cardiovascular autonomic control, especially as compared with responses by the hand cold-pressure test (2 min). RESULTS CO(2) projection in the left hand induced a steep decrease (-26 degrees C) in temperature followed by a rapid increase and a cutaneous vasoconstriction of the right hand, with significant increases in BP and cardiac parasympathetic activity. Cardiovascular responses were similar to those with application of the hand cold-pressure test. Application of an ice pack decreased cutaneous temperature to a lesser extent (-19 degrees C) and more slowly, without changing BP or indices of HR and BP variability. CONCLUSION CO(2) projection caused "thermal shock" and triggered a systemic cutaneous vasoconstriction response, with activation of indices of both ortho- and parasympathetic activity, as with the hand cold-pressure test. Vascular responses during ice pack cooling appeared solely localised to the cooled area, without any significant change in autonomic cardiovascular control.
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Affiliation(s)
- L Mourot
- Laboratoire de physiologie, faculté de médecine et de pharmacie, université de Franche-Comté, EA 3920 et IFR133, 25030 Besançon cedex, France.
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Iwasaki KI, Levine BD, Zhang R, Zuckerman JH, Pawelczyk JA, Diedrich A, Ertl AC, Cox JF, Cooke WH, Giller CA, Ray CA, Lane LD, Buckey JC, Baisch FJ, Eckberg DL, Robertson D, Biaggioni I, Blomqvist CG. Human cerebral autoregulation before, during and after spaceflight. J Physiol 2006; 579:799-810. [PMID: 17185344 PMCID: PMC2151354 DOI: 10.1113/jphysiol.2006.119636] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Exposure to microgravity alters the distribution of body fluids and the degree of distension of cranial blood vessels, and these changes in turn may provoke structural remodelling and altered cerebral autoregulation. Impaired cerebral autoregulation has been documented following weightlessness simulated by head-down bed rest in humans, and is proposed as a mechanism responsible for postspaceflight orthostatic intolerance. In this study, we tested the hypothesis that spaceflight impairs cerebral autoregulation. We studied six astronauts approximately 72 and 23 days before, after 1 and 2 weeks in space (n = 4), on landing day, and 1 day after the 16 day Neurolab space shuttle mission. Beat-by-beat changes of photoplethysmographic mean arterial pressure and transcranial Doppler middle cerebral artery blood flow velocity were measured during 5 min of spontaneous breathing, 30 mmHg lower body suction to simulate standing in space, and 10 min of 60 deg passive upright tilt on Earth. Dynamic cerebral autoregulation was quantified by analysis of the transfer function between spontaneous changes of mean arterial pressure and cerebral artery blood flow velocity, in the very low- (0.02-0.07 Hz), low- (0.07-0.20 Hz) and high-frequency (0.20-0.35 Hz) ranges. Resting middle cerebral artery blood flow velocity did not change significantly from preflight values during or after spaceflight. Reductions of cerebral blood flow velocity during lower body suction were significant before spaceflight (P < 0.05, repeated measures ANOVA), but not during or after spaceflight. Absolute and percentage reductions of mean (+/- s.e.m.) cerebral blood flow velocity after 10 min upright tilt were smaller after than before spaceflight (absolute, -4 +/- 3 cm s(-1) after versus -14 +/- 3 cm s(-1) before, P = 0.001; and percentage, -8.0 +/- 4.8% after versus -24.8 +/- 4.4% before, P < 0.05), consistent with improved rather than impaired cerebral blood flow regulation. Low-frequency gain decreased significantly (P < 0.05) by 26, 23 and 27% after 1 and 2 weeks in space and on landing day, respectively, compared with preflight values, which is also consistent with improved autoregulation. We conclude that human cerebral autoregulation is preserved, and possibly even improved, by short-duration spaceflight.
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Affiliation(s)
- Ken-ichi Iwasaki
- Institute for Exercise and Environmental Medicine, 7232 Greenville Avenue, Suite 435, Dallas, TX 75231, USA
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